hey guys today was a totally hot day i may. well that being said i have my ac on full blast. as i was pulling out of the parking lot, i hear this really loud chirping rattling noise coming from the engine bay. only problem is you only hear it when i put the car in gear. forward or back... but when i drive off, you dont hear it. only when ur at a stop and about to take off that noise happens. my ac blows fine, no engine light. the car drives fine, the car shifts fine. no signs of failure in any type of performance. just only at the initial take when pressing the gas, you here this loud rattling shirping noise. when i put the car in gear with the brakes on, the car makes that loud noise. i'll try to record it and have it posted soon. just hoping if anybody had this problem im describing. im afraid it may get worse. so i plan to take it to the shop this weekend.

I had my A/C compressor go out on me (less than a year after it was replaced). Before I took it to the stealer, I took it to Best Buy where they had just installed my head unit. I figured they had screwed up. When they couldn't find the problem and were driving it out of the bay, it chirp like a loose belt or tires rubbing against on a rubber floor. Then I took it to the stealer because I wasn't convinced Best Buy didn't screw up but then I thought it could also be the compressor which was still under warranty. It turned out that the sprag bearing took out the A/C compressor.

I don't know if the chirping is the death knell or if it still can be saved, but I have a new respect for that sound!

I don't want anybody to misunderstand and think that hearing that chirping sound absolutely means you are at risk of losing you A/C compressor, but it's not a sound to take lightly. I suspect that a slipping belt is probably fairly rare since there is a belt tensioner.

Sub'd.... I had the same noise just show up 3 days ago in my W211 E55. I am going to make a thread on it as well in the 211 AMG section. Please keep this post updated with any new findings.

will do.
just waiting for this weekend to take it in. its driveable but could be annoying at times when at a stop during idle and reversing. i really hope its not the compressor. my ac blows fine though. i hear a slight a rattle noise when i start the car and also when i step on the gas when i gear w/ the ac on. the chirping noise comes and goes, but louder during the day when its hot.

I had a brief experience with the noise (I only realized what it was in retrospect), but the chirp sounded similar. I can't say that it came on gradually (fewer chirps, then more) or all at once, or really under what conditions it was more prevalent. I don't know if something rather benign could also cause (possibly the belt tensioner is going out), but I did get a deep respect for that sound. I would find out whatever it is immediately.

As I told somebody on another thread, this is not something to play around with. I would take the car to someone who knows about the potential now and happily pay if it is nothing. If it is something that's dangerous, I'd get it fixed soon - unless you don't care about your A/C compressor.

So the car is finally in the shop. Just two days ago my a/c had this weird sucking noise and the blower wasnt blowing strong. just to get any air, i would have the knob set to #5. weird. So the mechanic says that i had a leak from the expansion tank hose and that may have caused the car to make that screaching noise. some plastic piece broke off from the heat is what they said. He then said i need a new water pump. Therefore i decided to just replace my belt and belt tensioner and idler at the same time. Lets just hope this fixes the problem. i'll keep you updated.